Industrial control systems have enabled modern factories to become partially or completely automated in many circumstances. These systems generally include a plurality of Input and Output (I/O) modules that interface at a device level to switches, contactors, relays and solenoids along with analog control to provide more complex functions such as Proportional, Integral and Derivative (PID) control. Communications have also been integrated within the systems, whereby many industrial controllers can communicate via network technologies such as Ethernet, Control Net, Device Net or other network protocols and also communicate to higher level computing systems. Industrial controllers utilize the aforementioned technologies along with other technology to control multiple applications ranging from complex and highly distributed to more traditional and repetitious applications.
At the core of the industrial control system, is a logic processor such as a Programmable Logic Controller (PLC). Programmable Logic Controllers are programmed by systems designers to operate manufacturing processes via user-designed logic programs or user programs. The user programs are stored in memory and generally executed by the PLC in a sequential manner although instruction jumping, looping and interrupt routines, for example, are also common. Associated with the user program are a plurality of memory elements or variables that provide dynamics to PLC operations and programs. These variables can be user-defined and can be defined as bits, bytes, words, integers, floating point numbers, timers, counters and/or other data types to name but a few examples.
Various remote applications or systems often attempt to update and/or acquire PLC information or related device information via a plurality of different, competing and often incompatible or insecure network technologies. A major concern with this type of access to PLC's and control systems in general, relates to the amount of security that is provided when sending or receiving data to and from the PLC. In most factories or industrial environments, complex and sometimes dangerous operations are performed in a given manufacturing setting. Thus, if a network-connected controller were inadvertently accessed, or even worse, intentional sabotage were to occur by a rogue machine or individual, potentially harmful results can occur.
One attempt at providing security in industrial control systems relates to simple password protection to limit access to the systems. This can take the form of a plant or controls Engineer or Administrator entering an alpha-numeric string that is typed by an operator each time access is attempted, wherein the controller grants access based on a successful typing of the password. These type passwords are highly prone to attack or discovery, however. Often times, users employ passwords that are relatively easy to determine (e.g., person's name or birthday). Sometimes, users exchange passwords with other users, whereby the password is overheard or simply, a user with improper authorization comes in contact with the password. Even if a somewhat higher level of security is provided, parties employing sophisticated hacking techniques can often penetrate sensitive control systems, whereby access should be limited to authorized users in order to mitigate potentially harmful consequences.